Liquid crystal displays (LCDs) have found widespread usage generally. LCD's have been employed in applications subject to significant temperature variations, including automobiles and airplanes. An LCDs performance is temperature-dependant, and in particular, performs poorly at low temperatures. Thus, heaters have been provided in LCD devices to raise the temperature of the LCD to achieve satisfactory functionality. The heaters have included LCD temperature sensors connected to a microprocessor which controls a switch to modulate the heater and maintain the LCD at a satisfactory operating temperature.
The microprocessor has also included logic to shut down the operation of the heater completely, if the temperature of the LCD becomes excessively elevated. Thus, a back-up mechanism has been provided to prevent overheating which might damage the LCD. One disadvantage of this back-up mechanism is it relies on the same microprocessor that is controlling the already malfunctioning heater control. Consequently, if the cause of the heater control malfunction is a failure of the microprocessor (or some other functional control component), it may also fail to activate the high temperature shut-off.